Follow these do's and don'ts in container gardening.
Master gardener Paul James offers tips for creating successful container gardens:
Don't forget to cover the drainage hole.
Water should be able to drain freely from the drain hole, which is why James doesn't suggest to cover it with stones or little pieces of broken clay pots. However, as important as it is for water to get out, you also don't want certain critters to get in. Sowbugs, or pillbugs, aren't especially troublesome but can do a number on strawberries and other plants. Earwigs can devastate plants. That's why he prefers to cover the drainage holes of pots with a piece of pantyhose (figure A) or window screen before filling them with potting mix.
Pack the potting mix when filling containers.
Potting mix tends to be fairly light, so if you don't pack it down as you add it to the pot, it will settle the first time you water. This can cause the rootballs of newly planted plants to become exposed and therefore susceptible to drying out.
Once you've filled your container about a third of the way full with potting mix, press it firmly with your hands (figure B). Then add another third and firm it again, and so on until ready to plant.
Tease the roots.
It's extremely important to loosen or tease the roots of plants (figure C) before sticking them in a pot, especially those that are rootbound. The process may look a bit extreme, but it's actually beneficial.
If you don't tease the roots, they'll just continue to grow in a circle rather than reach out into the surrounding potting mix. When that happens, the plants won't be able to absorb the surrounding water and nutrients, and they'll wilt and lack vigor.
Provide enough headroom.
When filling a container with potting mix, avoid adding the mix all the way up to the rim of the container. Without sufficient headroom at the top of the pot, water will run off rather than soak into the pot. Instead, leave at least an inch of headroom below the rim of the pot (figure D) so thirsty plants will have an opportunity to drink the water.
Water newly potted plants right away--then water again.
The initial watering will likely run out of the drainage hole quickly because of all the pore spaces in the potting mix. However, the mix will settle within a few minutes, at which time it's a good idea to water again slowly, allowing the mix to soak up all the moisture.
Container-grown plants benefit from a light layer of mulch. This is especially true for those that are grown in terra-cotta pots, which tend to lose moisture fairly quickly due to the porous nature of the clay.
When mulching plants in containers, the trick is to match the mulch to the plant. This hydrangea (figure E) prefers steady moisture and acidic soil, so a one-inch layer of sphagnum moss is ideal. The moss will keep the soil moist between waterings and slowly acidify the soil as well.
At the other extreme, the cacti and succulents in this trough (figure F) prefer dry soil and a nearly-neutral, slightly-alkaline soil. In this case, a mulch of pea gravel is perfect because it lets the moisture evaporate and keeps the pH within the ideal range. What's more, the lightly-colored gravel reflects the sun, thereby giving these plants the warm environment in which they thrive.
Similarly, you can use a light layer of sand to mulch cacti and succulents. Sand mulch can also help control the gnats that sometimes seem to pop out of nowhere.
Also in the house, decorative, polished stones (figure G) can give containerized houseplants a little something extra. Or you might consider bark mulch made specifically for houseplants.
There's always shredded bark mulch (figure H). It works nicely on container plants and enhances their overall look.
For plants that are prone to slug attack, consider crushed pecan shells (figure I) because slugs don't like to move across their jagged edges. For something a bit more exotic, try crushed cocoa shells. They also deter slugs and look great. What's more, they smell just like chocolate.
Yet another great mulch worthy of consideration is moss. Whether it's sphagnum, Spanish (figure J), or sheet moss, these mosses are all available for purchase in bags.
And finally, try this new mulching material--a bag full of terra-cotta balls. Placed around the base of a container plant, especially one in which the base of the plant is highly visible, these balls add a unique decorative touch to a container (figure K).